Why can you hear the ocean
when holding a seashell to your ear?
Do you remember trying this as a
kid -- Holding one of the seashells you grabbed as a souvenir up to your ear?
It seems like no matter how far away from the ocean you are, you can still
hold a seashell up to your ear and hear the roar of the waves rolling onto the
shore. The best shells for producing this sound are the large, spiral conch
Some people have suggested that the
sound you hear from the seashell is the echoing of your blood rushing through
blood vessels of your
ear. That is not the case. If that were true, then the sound would intensify
after exercising, since your blood races faster after exercising. However, the
sound is the same even after exercising.
Others say that the whooshing sound
inside the shell is generated by air flowing through the shell - air flowing
through the shell and out creates a noise. You'll notice that the sound is
louder when you lift the shell slightly away from your ear than it is when the
shell is right against your head. However, this theory doesn't hold true in a
soundproof room. In a soundproof room, there is still air, but when you hold
the seashell to your ear, there's no sound.
The most likely explanation for the
wave-like noise is ambient noise from around you. The seashell that you are
holding just slightly above your ear captures this noise, which resonates
inside the shell. The size and shape of the shell therefore has some effect on
the sound you hear. Different shells sound different because different shells
accentuate different frequencies. You don't even need the seashell to hear the
noise. You can produce the same "ocean" sound using an empty cup or even by
cupping your hand over your ear. Go ahead and try it and vary the distance at
which you place the cup near your ear. The level of the sound will vary
depending on the angle and distance the cup is from your ear.
Noise from outside the shell also
can change the intensity of the sound you hear inside the shell. You can look
at the shell as a resonating chamber. When sound from outside enters the
shell, it bounces around, thus creating an audible noise. So, the louder the
environment you are in, the louder the ocean-like sound will be.